Windows Azure VM doesn't save IP address after shut down

I created 3 VM in windows azure with following IPs assigned by DHCP after creation:

VM1 - 192.168.10.4

VM2 - 192.168.10.5

VM3 - 192.168.10.6

After a time I shut down the VMs. In about two days I started them again in the following order: VM2, VM3, VM1. And after this I've found the following IPs:

VM2 - 192.168.10.4

VM3 - 192.168.10.5

VM1 - 192.168.10.6

Microsoft says: "dynamic IP addresses of Windows Azure virtual machines that are attached to a Windows Azure Virtual Network persist for the lifetime of the virtual machine"

Why the IP addresses were changed?

P.S. We have cross-site VPN between Azure and on-premise environment.